Collapsible truss structure

ABSTRACT

A metal truss structure is disclosed which is prefabricated and capable of being shipped in a collapsed condition in which it occupies a space on the order of four inches by four inches by twenty-eight feet, and which can be erected easily at the site into a roof truss capable of spanning all widths common in residential structures and some commercial structures, while maintaining a desired and predetermined roof pitch, as for example 4:12. A half truss suitable for panelized construction or for modular construction, and having many of the features of the basic truss structure, is also disclosed.

United States Patent [191 Mueller et al.

[ Sept. 25, 1973 COLLAPSIBLE TRUSS STRUCTURE [73] Assignee: Armco SteelCorporation,

Middletown, Ohio [22] Filed: Jan. 20, 1972 [21] Appl. No.: 219,254

521 user. 52/641 51 1m.c| E04b7/16 [58] Field of Search 52/641,645, 640,

[56] References Cited UNITED STATES PATENTS 3,062,340 1l/l962 Hunnebeck52/655 X 2,642,825 6/1953 McEllone et al. 52/641 FOREIGN PATENTS ORAPPLICATIONS 483,168 i938 Great Britain 52/l09 839,854 1952 Germany52/640 Primary Examiner-Frank L. Abbott Assistant ExaminerCarl D.Friedman Attorney-John W. Melville et al.

[57] ABSTRACT A metal truss structure is disclosed which isprefabricated and capable of being shipped in a collapsed condition inwhich it occupies a space on the order of four inches by four inches bytwenty-eight feet, and which can be erected easily at the site into aroof truss capable of spanning all widths common in residentialstructures and some commercial structures, while maintaining a desiredand predetermined roof pitch, as for example 4: 12. A half trusssuitable for panelized construction or for modular construction, andhaving many of the features of the basic truss structure, is alsodisclosed.

17 Claims, 23 Drawing Figures PATENTEDSEPZSIHH 3,760,550

SHEEI 2 BF 4 1 COLLAPSIBLE TRUSS STRUCTURE BACKGROUND OF THE INVENTIONThe building of roof trusses on the building site in residential and insmall commercial buildings is an expensive and time consuming operation.In addition, where a large number of such trusses need be built, theyrarely turn out to be perfectly uniform. As a result, the buildingindustry has gone to the prefabricated roof truss which eliminates thecostly on-site labor time. When these prefabricated wooden trusses arecompletely assembled, a special truck is required for shipping them tothe job site and one such truck can usually just about carry the numberof trusses required for a single home. Because of the shape of theassembled trusses and the configuration of the special truck which mustbe used, it is impossible to carry any additional constructionmaterials. Furthermore, such prefabricated trusses must be ordered tosize for each individual structure. With trusses of longer spans theweight of the assembled wood trusses becomes excessive since it isnecessary to use heavier wood members. In fact, the relatively few sizesof standard lumber available often results in a structure which isover-adequate for the intended purpose.

A complete truss according to the present invention occupies an area ofabout four inches by four inches by twenty-eight feet when fullycollapsed, so that many such trusses can be stacked easily on anordinary flatbed truck or trailer which may also be used for thedelivery of bulk materials. Since the truss of this invention is capableof use for any commonly used span, such trusses may be ordered in largequantities and stockpiled for future use and need not be speciallyordered and built for each particular building.

The use of trusses according to the present invention makes it possibleto optimize the steel members which make up the truss for the loadrequirements involved and thus one is not limited to standard availablesizes. This factor combined with the increased modulus and strength ofsteel over wood results in a noticeably lighter truss which is thereforeeasier to handle during erection.

Beyond the provision of collapsible trusses per se, the invention alsocontemplates a panelized construction and a modular construction. In apanelized construction a plurality of half trusses according to theinvention are assembled with a roof decking or sheathing so that at thesite the several trusses may be erected to provide a complete roof. In amodular construction, the half trusses are assembled with roof decking,a side wall, and half end walls; and plumbing, duct work, and electricalwiring are all installed at the factory. Thus, two such modular halfbuildings may be assembled at the site into a complete building.

BRIEF SUMMARY According to the invention, a full truss comprises abottom chord member, a top chord member, and two web members on eachside of the middle. The chord members are steel channel members and havetelescoping extensions at their outer ends. The telescoping extensionsare pivotally connected. In a full truss, the upper chord member isprovided in two pieces of half length which may be mitered at theiradjacent ends to provide a desired pitch, say 4:12 for the roof; andthey are held together by a strap of relatively thin bendable material.Extensions are provided for the chord members so the truss may be usedfor a variety of spans, while still maintaining the predetermined pitch.On each side of middle there are provided two web members in a Vconfiguration. One arm of each V is pivotably secured at its upper endadjacent the inner end of the respective upper chord piece. The upperend of the other arm of the V is pivotably secured to an element whichis slidable along the respective upper chord piece. The lower ends ofthe Vs on each side are pivotably secured to each other, and to membersslidable along the lower chord on each side of center. While thestructure above outlined provides a symmetrical truss, it will beunderstood that for some structures it may be desirable to provide upperchord pieces of unequal length.

Thus, the complete truss may constitute in its collapsed condition apackage having dimensions of about four inches by four inches bytwenty-eight feet. By lifting'up the adjacent inner ends of the topchord pieces, thereby bending the connecting strap, the web membersadjust themselves by sliding along the upper and lower chords until thepredetermined pitch is attained, and the extensions in the upper chordmembers also adjust themselves. In this manner, a truss ofminimum spanis produced. If a longer span is required, the extension members in thelower chord member are first extended equally from each end until thedesired span is reached, and then fixed at these locations by suitablemeans, such as self-threading I screws. Erecting into final conditioncontinues as previously described, resulting in a truss having anincreased span, but with the same predetermined and desired pitch. Whenthe truss is thus fully erected, the several remaining slidable partsare also fixed in position by suitable means, as for example,self-threading screws.

The half truss, whether for use for the panelized construction or amodular construction as above outlined, is basically one half of acomplete truss; and the half trusses for the two types of constructionare basically similar, with minor variations.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG. 1 is a planview of a full truss in fully collapsed condition.

FIG. 1A is an elevational view showing the truss in partially erectedcondition.

FIG. 1B is a view similar to FIG. 1A showing the truss in a further,butstill partially erected condition.

FIG. 1C is an elevational view showing the truss in fully erectedcondition.

FIG. 2 is a cross sectional view on an enlarged scale, taken on the line22 of FIG. 1C.

FIG. 3 is a fragmentary perspective view of the joint between the upperand lower chord extensions.

FIG. 4 is a fragmentary cross sectional view taken on the line 44 ofFIG. 1C.

FIG. 5 is a perspective view of the structure shown in FIG. 4.

FIG. 6 is a perspective view of an insert which may be used at the jointbetween the two upper chords.

FIG. 7A is a fragmentary perspective view of the two upper chords withthe insert of FIG. 6 in place, the truss being in its collapsedcondition.

FIG. 7B is a view similar to FIG. 7A showing the condition when thetruss is erected.

FIG. 8A is an elevational view of the two upper chords showing amodification, the chords being in collapsed condition.

FIG. 8B is a view similar to FIG. 8A showing the condition when thetruss is erected.

FIG. 9 is a plan view of a half truss suitable for panelizedconstruction, in collapsed condition.

FIG. 10 is an elevational view of the half truss in erected condition.

FIG. 11 is a fragmentary end elevational view of the connection betweenthe upper and lower chords, as seen from the left of FIG. 10.

FIG. 12 is a plan view of a modified half truss, suitable for modularconstruction, in collapsed condition.

FIG. 13 is an elevational view of the half truss of FIG. 12 in partiallyerected condition.

FIG. 14 is an elevational view of the same half truss in fully erectedcondition.

FIG. 15 is a cross sectional view, on an enlarged scale, taken on theline 15-15 of FIG. 14.

FIG. 16 is a cross sectional view taken on the line 16-16 of FIG. 14.

FIG. 17 is a view similar to FIG. 8A, showing a modification.

FIG. 18 is a view similar to FIG. 8B, showing the same modification.

DETAILED DESCRIPTION Referring first to FIGS. 1 to 8B which disclose afull truss according to the invention, the collapsed truss package isshown at 10 in FIG. 1. For most purposes, this package will be fourinches by four inches by twenty-eight feet. It is assumed that the trussis designed for a conventional roof pitch of 4:12, but it should benoted that any pitch desired in the intended construction is possible.The progressive erection of truss from the condition of FIG. 1 to thecondition of FIG. 1C is shown in FIGS. 1A, 1B and 1C.

Basically, the truss consists of a bottom chord indicated generally at13 and an upper chord consisting of two pieces 14 and 14a. These chordpieces are all in the form of channel members having lipped or returnflanges and the pieces 14 and 14a may be joined together at theiradjacent ends by a strap member 15 of relatively thin bendable material.

In the embodiment shown, the bottom chord 13 is provided with thetelescoping extensions 16 and 16a and the upper chord pieces 14 and 140are provided with the telescoping extensions 17 and 17a, respectively.The extension members 16, 16a, 17, and 17a are in the form of plainchannels without the lipped flanges. These members are disposedback-to-back and are dimpled at the center as indicated at 17b and 16bin FIG. 2 and they are secured together by means of a bolt 25 passingthrough the aligned openings 18. It will be understood that thesemembers can also be fastened with rivets, or self-drilling screws. Thisis true for any bolted connection described herein.

On each side of the middle there are a pair of webs in a Vconfiguration. Thus, there are the relatively short web members 19 and20 and the relatively long web members 21 and 22. The upper ends of theweb members 21 and 22 are pivotably secured to the respective upperchord pieces 14 and 14a. This connection is pivotable but not slidable.The upper ends of the web members 19 and 20 are pivotably connected tosliding channel elements 23 by means of bolts 24 as best seen in FIGS. 4and 5, where a typical construction connecting the upper end of the web19 is shown. The end of the web member 19 is dimpled as at 19a and thebolt 24 is passed through the openings in the member 23 and in thecenter of the dimple 19a. It will be understood that the constructionshown in FIGS. 4 and 5 is found at the upper end of each of the webs l9and 20.

The lower ends of the webs l9 and 20 are pivotably secured to a similarsliding channel member and to the lower ends of the webs 21 and 22respectively.

From the foregoing description it will be clear that as the truss iserected from the condition of FIG. 1 to the condition of FIG. 1C, thestrap member 15 is bent. It should also be noted that the inner ends ofthe truss pieces 14 and 14a may be mitered as shown respectively at 14band 140, so that the miter defines the limit to which the truss may beerected and defines the desired roof pitch. Another method of connectingtruss pieces 14 and 14a, which does not necessitate mitering of the endsof the truss pieces, will be described hereinafter. As the truss iserected and as can be seen very clearly in the progression of FIGS. 1A,1B, and 1C, the bottom of the V structure of the web 19, 21 and 20, 22slides along the chord 13 and similarly the sliding members 23 at theupper ends of the webs l9 and 20 slide along the chord pieces 14 and14a.

As described above the extension members l6, l7 and 16a, 17a arepivotably secured together by means of the bolts 25 and it will beunderstood that by extending the telescoping members 16, 17, 16a, theheight of the truss and the span of the truss are increased withoutdisturbing the desired roof pitch. Thus, a truss according to thisinvention may be manufactured to serve for a variety of spans and infact such a truss can be made to cover all of the commonly used spanswhich are found in residential and small comm ercial buildings.

Once the truss has been erected to the required span the various slidingelements are simply fixed in position by means of sheet metal screws orother suitable fastening. A typical fastening arrangement using sheetmetal screws is shown at 26 in FIGS. 4 and 5. Similarly, of course, theextensions 16, 17, 16a and 17a will also be secured with sheet metalscrews or the like and the sliding members at the bottom of the Vconfigurated webs will be similarly fixed.

The ridge portion of the truss may be fixed and secured in several ways,two of which are shown in the drawings. In FIG. 6 there is shown achannel member 27 having its web centrally slotted at 28 and relieved at29. It is also provided with the predrilled holes 30. The element ofFIG. 6 is shown in position in the collapsed truss in FIG. 7A. When thetruss is erected the insert member 27 bends along the line 31 and theadjacent portions of the web of the member 27 overlap each other asclearly seen in FIG. 7B. The two lower holes 30 coincide when thepredetermined angular relation is established and a bolt 32 secures theupper chord pieces 14 and 14a in position. The remaining holes 30 serveto fasten the upper ends of the web members 21 and 22, respectively. Itshould be noted that in this embodiment the inner ends of the upperchord members 14 and 14a are separated, and are connected by means ofthe insert 27, so that mitering is unnecessary.

An alternative construction is shown in FIGS. 8A and 8B. Here a smallplate 33 is provided which is bolted to one of the chord pieces, in thisinstance the piece 14 at 34. Thus, when the truss is erected the partsgo from the position shown in FIG. 8A to the position shown in 88 and abolt is then inserted through the holes 35 and 36 which will now bealigned. It should be noted that the inner ends of the chord members 14and 140 are mitered, as shown respectively at 14b and 140, so that themiter defines the limit to which the truss may be erected, and definesthe desired roof pitch.

A still further embodiment is illustrated in FIGS. 17 and 18, wherein aone-piece upper chord is disclosed. The one-piece upper chord 81 has itsweb, lower flange and upper and lower lips cut out, as indicated at 82and 83, leaving its upper flange only along the line 84. The angles ofthe cuts 82 may be such as to determine the roof pitch, or they may begreater, and a connector piece may be relied upon to determine thepitch. A connector such as that shown in FIGS. 8A and 8B may be used,either to determine the pitch and fix the truss parts in position, orsimply to fix the truss parts in position.

Coming now to a description of a half truss and particularly a halftruss suitable for use in a panelized construction, reference is made toFIGS. 9 to 11 inclusive. Again, the half truss 50 is shown in acollapsed condition in FIG. 9. It consists of a bottom chord 51 and atop chord 52. Itshould be noted that inFIGS. 9 to 11, no extensionmembers are shown for the chord pieces 51 and 52 but it will be clearthat they may be added in the same manner as disclosed in connectionwith FIGS. 2 and 3. The web members are shown at 53 and 54. Again theweb member 54 is pivotably bolted to the end of the upper chord 52 at 55and the lowerv ends of the webs 53 and 54 are pivotably secured to eachother and to a sliding member at 56. The upper end of the web member 53is secured to a sliding member 57 in the same manner as was described inconnection with FIG. 5. A web stop is provided at the inner end of thelower chord 51 at 58. Since the channels constituting the chords 51 and52 open toward each other in order to provide the tracks in which thesliding pieces 56 and 57 travel, an insert 59 is secured within thechannel 51 and a-plate 60 is secured to the channel 52 so that thechannels 51 and 52 may be pivotably connected to each other. The partsare connected together by a bolt 61. In this way a neat boxlikestructure is provided for the collapsed half truss.

When the half truss is collapsed, the sliding member 57 slides towardthe-left in the upper chord 52 and the sliding connection at the bottomof the webs 53 and S4 slide toward the left in the chord 51.

In a panelized construction roof decking or sheathing is applied to aplurality of such half trusses and thus a half roof may be shippeddirect to the site in collapsed condition. When such a half roof arrivesat the site, the plurality of half trusses having the roof deckingattached thereto are erected to the position of FIG. with the slidingconnection at the lower ends of the webs 53 and 54 abutting against theweb stop 58. The parts are then fixed in position as described inconnection with the full truss and a half roof including truss anddecking is provided.

The building industry is now coming to a modular construction whereinsubstantially a half building is prefabricated including a side wall,two ends walls, half roof trusses, and roof decking, and with duct work,plumbing, and electrical work already installed. For such a purpose, thestructure of FIGS. 9 to 11 is slightly modified. Again, the collapsedhalf truss for modular use is shown in FIG. 12 at 70. FIG. 13 shows thehalf truss in a partially erected condition for a purpose to bedescribed later, and FIG. 14 shows the half truss in its fully erectedcondition. In this instance, the upper chord consists of a main portion71 and a telescoping extension 72 at its upper end. The lower chordconsists of a main portion 73 and a telescoping extension 74 at itsouter end. It should be noted that these telescoping extensions 72 and74 are at opposite ends of the respective chord members.

The web members 76 and may be in all respects just like those indicatedat 53 and 54 respectively in connection with FIGS. 9 to 11. Again, anend stop is provided at 77 and an intermediate stop is provided at 78 inthe lower chord.

With the half truss in the condition of FIG. 14, all of the assemblywork at the factory is done. The side wall and end walls of the buildingare attached and the various elements of duct work, electrical, andplumbing work are installed.

Difficulty is encountered when such a module is to be shipped from thefactory where it is assembled, to the building site. This inventionmakes it possible to partially collapse the assembled half roof trussand to make it narrower and lower for shipment purposes. Thus, when theextensions 72 and 74 are telescoped respectively into the members 71 and73 and the web members 75 and 76 are caused to move to the left asdescribed above, the half truss may assume the position shown in FIG. 13where the connection between the web member 75 and 76 to the slidingmember 79 abuts against the intermediate stop 78 to hold the partiallycollapsed half truss in the condition of FIG. 13. In this condition, itmay be seen that the half truss is substantially narrower and lower thanin its erected condition and is in fact no longer than it was in itsfully collapsed condition of FIG. 12. The state of the half truss inFIG. 13 does not interfere with duct work and piping and the likeinstalled under the roof and yet the half truss is now of small enoughsize that it can be handled with presently available trucks withoutviolating laws in regard to width and height of loads traveling overhighways.

Again, as shown in FIG. 15, the members 71 and 73 are disposed withtheir openings facing each other and for this reason the member 71 isprovided with a plate 71a having the dimple 71b so that the connectionbetween the upper chord 71 and the lower chord extension 74 can be madeby means of bolting through the opening 80. The connection between theupper chord extension 72 and the web 75 is shown in FIG. 16.

It will be seen that the construction of FIGS. 9- to 11, which has beendescribed for a panelized construction and the construction of FIGS. 12'to 16 which has been described as for a modular construction, are inreality very similar, and there will undoubtedly be instances whereeither construction may be used. An additional advantage of bothconstructions is that they may be erected from the right hand end asseen in these Figures, thus permitting workmen to effect erection fromoutside the construction. In connection with a modular construction,this is of great importance.

It will be understood that numerous modifications may be made in detailsof the construction without departing from the spirit of the invention.No limitation not specifically set forth in the claims is intended andnone should be implied.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A roof truss comprising an upper chord and a lower chord, eachconstituted by channel members having lipped flanges, and a pair of webmembers extending therebetween, said web members at their lower endsbeing pivotably connected together and to an element slidable along saidlower chord, one of said web members, at its upper end, being pivotablyconnected to said upper chord adjacent the inner end thereof, and theother of said web members, at its upper end, being pivotably connectedto an element slidable along said upper chord, said slidable elementsbeing plain channel pieces slidable within said lipped channel members,whereby said truss, in collapsed condition, presents a long, thin andnarrow package, and is capable of being erected, with said slidableelements adjusting themselves along the respective chords, said slidableelements then being secured in fixed position.

2. A truss according to claim I, wherein said upper and lower chords areprovided with extensions telescopingly arranged with respect to saidchords, and said extensions, at their outer ends are pivotably connectedtogether.

3. A truss according to claim 2, wherein said chords are constituted bychannel members having lipped flanges, and said extensions are plainchannel pieces slidable within said lipped channel members.

4. A roof truss comprising a one-piece lower chord and an upper chordcomposed of two portions secured together at the middle of the truss, apair of web members on each side of the middle, each pair of web membersat their lower ends being pivotably secured together and to an elementslidable along said lower chord, one of the web members of each pair, atits upper end, being pivotably connected to the respective upper chordportion adjacent the middle of the truss, and the other web member ofeach pair, at its upper end, being pivotably connected to an elementslidable along the respective upper chord portion, whereby said truss,in collapsed condition, presents a long, thin and narrow package, and iscapable of erection by raising the middle of the upper chord, with saidslidable elements adjusting themselves along the respective chords, saidslidable elements then being secured in fixed position.

5. A truss according to claim 4, wherein said upper chord portions attheir adjacent ends, are mitered to provide a desired, predeterminedroof pitch, and are held together by a strap of thin bendable material.

6. A truss according to claim 5, wherein a connector element is providedto secure said upper chord portions in the position providing saiddesired roof pitch.

7. A truss according to claim 4, wherein the inner ends of said upperchord portions are spaced apart, and connected together by a channelshaped insert engaging in and secured to, the proximate ends of saidchord portions, said insert having its web slotted, and having its lowerflange and the lower portion of the web relieved, whereby duringerection of the truss, the portions of the insert web separated by saidslot overlap each other, a hole in said web on each side of said slot,said holes being located such that they will coincide when the desiredroof pitch is attained, and may be fixed in position by fastening meanspassing through said aligned holes.

8. A truss according to claim 4, wherein said chords are constituted bychannel members having lipped flanges, and said slidable elements areplain channel pieces slidable within said lipped channel members.

9. A truss according to claim 4, wherein said upper and lower chords areprovided with extensions telescopingly arranged with respect to saidchords.

10. A truss according to claim 9, wherein said extensions are providedat the outer ends of the upper and lower chords, and said extensions, attheir outer ends, are pivotably connected together.

11. A truss according to claim 9, wherein said chords are constituted bychannel members having lipped flanges, and said extensions are plainchannel pieces slidable within said lipped channel members.

12. A half roof truss comprising an upper chord and a lower chord, eachconstituted by channel members having lipped flanges, and a pair of webmembers extending therebetween, said web members at their lower endsbeing pivotably connected together and to an element slidable along saidlower chord, one of said web members, at its upper end, being pivotablyconnected to said upper chord adjacent the inner end thereof, and theother of said web members, at its upper end, being pivotably connectedto an element slidable along said upper chord, said slidable elementsbeing plain channel pieces slidable within said lipped channel members,and stop means for said first named slidable element at the inner end ofsaid lower chord, whereby said half truss, in collapsed condition,presents a long, thin and narrow package, and is capable of beingerected, with said slidable elements adjusting themselves along theirrespective chords, said slidable elements being then secured in fixedposition.

13. A roof truss according to claim 4, wherein said upper chord is aone-piece member, said chords being constituted by lipped channelmembers, said upper chord having its web, its lower flange and lip, andits upper lip relieved, and its upper flange having a line of weaknesstransversely of the length of said chord, whereby said upper chord maybe bent along said line of weakness to provide a ridge, and a connectorelement to secure the relieved parts together in an angular relation.

14. A truss according to claim 12, wherein said upper and lower chordsare provided with extensions telescopingly arranged with respect to saidchords, and said extensions, at their outer ends are pivotably connectedtogether.

15. A truss according to claim 14, wherein said chords are constitutedby channel members having lipped flanges, and said extensions are plainchannel pieces slidable within said lipped channel members.

16. A truss according to claim 12, wherein each of said chords iscomposed of a major piece and a minor extension piece in telescopingrelation, the combined length of each major piece and minor extension,when extended, constituting the length of said upper and lower chordsrespectively, the upper chord having its extension piece at its innerend, and the lower chord having its extension piece at its outer end,the outer end of the major piece of said upper chord being pivotablysecured to the outer end of the extension piece of the said lower chord,a pair of web members extending between said chords, said web members,at their lower ends, being pivotably connected together and to anelement slidable along the major piece of said lower chord, one of saidweb members, at its upper end, being pivotably connected to the end ofthe extension piece of the said upper chord, and the other of said webmembers at its upper end being pivotably connected to an elementslidable along the major piece of said upper chord, and stop means atthe inner end of the major piece of said lower chord, whereby said trussin fully collapsed condition presents a long, thin and narrow packageand is capable .of being erected with said first named slidable elementresting against said stop means, and said extension pieces fullyextended, said second within said lipped channel members.

1. A roof truss comprising an upper chord and a lower chord, eachconstituted by channel members having lipped flanges, and a pair of webmembers extending therebetween, said web members at their lower endsbeing pivotably connected together and to an element slidable along saidlower chord, one of said web members, at its upper end, being pivotablyconnected to said upper chord adjacent the inner end thereof, and theother of said web members, at its upper end, being pivotably connectedto an element slidable along said upper chord, said slidable elementsbeing plain channel pieces slidable within said lipped channel members,whereby said truss, in collapsed condition, presents a long, thin andnarrow package, and is capable of being erected, with said slidableelements adjusting themselves along the respective chords, said slidableelements then being secured in fixed position.
 2. A truss according toclaim 1, wherein said upper and lower chords are provided withextensions telescopingly arranged with respect to said chords, and saidextensions, at their outer ends are pivotably connected together.
 3. Atruss according to claim 2, wherein said chords are constituted bychannel members having lipped flanges, and said extensions are plainchannel pieces slidable within said lipped channel members.
 4. A rooftruss comprising a one-piece lower chord and an upper chord composed oftwo portions secured together at the middle of the truss, a pair of webmembers on each side of the middle, each pair of web members at theirlower ends being pivotably secured together and to an element slidablealong said lower chord, one of the web members of each pair, at itsupper end, being pivotably connected to the respective upper chordportion adjacent the middle of the truss, and the other web member ofeach pair, at its upper end, being pivotably connected to an elementslidable along the respective upper chord portion, whereby said truss,in collapsed condition, presents a long, thin and narrow package, and iscapable of erection by raisiNg the middle of the upper chord, with saidslidable elements adjusting themselves along the respective chords, saidslidable elements then being secured in fixed position.
 5. A trussaccording to claim 4, wherein said upper chord portions at theiradjacent ends, are mitered to provide a desired, predetermined roofpitch, and are held together by a strap of thin bendable material.
 6. Atruss according to claim 5, wherein a connector element is provided tosecure said upper chord portions in the position providing said desiredroof pitch.
 7. A truss according to claim 4, wherein the inner ends ofsaid upper chord portions are spaced apart, and connected together by achannel shaped insert engaging in and secured to, the proximate ends ofsaid chord portions, said insert having its web slotted, and having itslower flange and the lower portion of the web relieved, whereby duringerection of the truss, the portions of the insert web separated by saidslot overlap each other, a hole in said web on each side of said slot,said holes being located such that they will coincide when the desiredroof pitch is attained, and may be fixed in position by fastening meanspassing through said aligned holes.
 8. A truss according to claim 4,wherein said chords are constituted by channel members having lippedflanges, and said slidable elements are plain channel pieces slidablewithin said lipped channel members.
 9. A truss according to claim 4,wherein said upper and lower chords are provided with extensionstelescopingly arranged with respect to said chords.
 10. A trussaccording to claim 9, wherein said extensions are provided at the outerends of the upper and lower chords, and said extensions, at their outerends, are pivotably connected together.
 11. A truss according to claim9, wherein said chords are constituted by channel members having lippedflanges, and said extensions are plain channel pieces slidable withinsaid lipped channel members.
 12. A half roof truss comprising an upperchord and a lower chord, each constituted by channel members havinglipped flanges, and a pair of web members extending therebetween, saidweb members at their lower ends being pivotably connected together andto an element slidable along said lower chord, one of said web members,at its upper end, being pivotably connected to said upper chord adjacentthe inner end thereof, and the other of said web members, at its upperend, being pivotably connected to an element slidable along said upperchord, said slidable elements being plain channel pieces slidable withinsaid lipped channel members, and stop means for said first namedslidable element at the inner end of said lower chord, whereby said halftruss, in collapsed condition, presents a long, thin and narrow package,and is capable of being erected, with said slidable elements adjustingthemselves along their respective chords, said slidable elements beingthen secured in fixed position.
 13. A roof truss according to claim 4,wherein said upper chord is a one-piece member, said chords beingconstituted by lipped channel members, said upper chord having its web,its lower flange and lip, and its upper lip relieved, and its upperflange having a line of weakness transversely of the length of saidchord, whereby said upper chord may be bent along said line of weaknessto provide a ridge, and a connector element to secure the relieved partstogether in an angular relation.
 14. A truss according to claim 12,wherein said upper and lower chords are provided with extensionstelescopingly arranged with respect to said chords, and said extensions,at their outer ends are pivotably connected together.
 15. A trussaccording to claim 14, wherein said chords are constituted by channelmembers having lipped flanges, and said extensions are plain channelpieces slidable within said lipped channel members.
 16. A trussaccording to claim 12, wherein each of said chords is composed of amajor piece and a minor extension piece in telescoping relation, thecombined length of each major piece and minor extension, when extended,constituting the length of said upper and lower chords respectively, theupper chord having its extension piece at its inner end, and the lowerchord having its extension piece at its outer end, the outer end of themajor piece of said upper chord being pivotably secured to the outer endof the extension piece of the said lower chord, a pair of web membersextending between said chords, said web members, at their lower ends,being pivotably connected together and to an element slidable along themajor piece of said lower chord, one of said web members, at its upperend, being pivotably connected to the end of the extension piece of thesaid upper chord, and the other of said web members at its upper endbeing pivotably connected to an element slidable along the major pieceof said upper chord, and stop means at the inner end of the major pieceof said lower chord, whereby said truss in fully collapsed conditionpresents a long, thin and narrow package and is capable of being erectedwith said first named slidable element resting against said stop means,and said extension pieces fully extended, said second named slidableelement adjusting itself along said upper chord, and said truss alsobeing capable of being partially collapsed, there being an intermediatestop member in the major portion of said lower chord whereby said trussmay be partially collapsed and the telescoping extensions withdrawn topresent a relatively low and relatively narrow package for shipment. 17.A truss according to claim 16, wherein the major pieces of said chordsare constituted by channel members having lipped flanges, and saidslidable elements and extension pieces are plain channel pieces slidablewithin said lipped channel members.